According to Sunni tradition, Muhammad did not clearly designate a successor and the Muslim community acted according to his sunnah in electing his father-in-law Abu Bakr as the first caliph.[2] This contrasts with the Shi'a view, which holds that Muhammad intended his son-in-law and cousin Ali ibn Abi Talib to succeed him.[3][4] Political tensions between Sunnis and Shias continued with varying intensity throughout Islamic history and they have been exacerbated in recent times by ethnic conflicts and the rise of Wahhabism.[2]

As of 2009[update], Sunni Muslims constituted 87–90% of the world's Muslim population.[5] Sunni Islam is the world's largest religious denomination, followed by Catholicism.[6][7] Its adherents are referred to in Arabic as ahl as-sunnah wa l-jamāʻah ("the people of the sunnah and the community") or ahl as-sunnah for short. In English, its doctrines and practices are sometimes called Sunnism,[8] while adherents are known as Sunni Muslims, Sunnis, Sunnites and Ahlus Sunnah. Sunni Islam is sometimes referred to as "orthodox Islam".[9][10][11]

Sunnī (Classical Arabic: سُنِّي/ˈsunniː/), also commonly referred to as Sunnīism, is a term derived from sunnah (سُنَّة/ˈsunna/, plural سُنَنsunan/ˈsunan/) meaning "habit", "usual practice",[12] "custom", "tradition". The Muslim use of this term refers to the sayings and living habits of the prophet Muhammad. In Arabic, this branch of Islam is referred to as ahl as-sunnah wa l-jamāʻah (Arabic: أهل السنة والجماعة‎‎), "the people of the sunnah and the community", which is commonly shortened to ahl as-sunnah (Arabic أهل السنة).

One common mistake is to assume that the Sunni denomination represents Islam as it existed before the divisions, and should be considered as normative, or the standard.[13] This perception is partly due to the reliance on highly ideological sources that have been accepted as reliable historical works, and also because the vast majority of the population is Sunni and this narrative suits their denomination, even though it is far from accurate. Both Sunnism and Shiaism are the end products of several centuries of competition between ideologies. Both sects used each other to further cement their own identities and divisions.[14]

The first four caliphs are known among Sunnis as the Rashidun or "Rightly-Guided Ones". Sunni recognition includes the aforementioned Abu Bakr as the first, Umar who established the Islamic calendar as the second, Uthman as the third, and Ali as the fourth.[15] The sequence of events of the 20th century has led to resentment in some quarters of the Sunni community due to the loss of pre-eminence in several previously Sunni-dominated regions such as the Levant, Mesopotamia, the Balkans and the Caucasus.[16]

Sunnis believe that the companions of Muhammad were the best of Muslims. This belief is based upon prophetic traditions such as one narrated by Abdullah, son of Masud, in which Muhammad said: "The best of the people are my generation, then those who come after them, then those who come after them." Support for this view is also found in the Quran, according to Sunnis.[18] Sunnis also believe that the companions were true believers since it was the companions who were given the task of compiling the Quran. Furthermore, narrations that were narrated by the companions (ahadith) are considered by Sunnis to be a second source of knowledge of the Muslim faith. A study conducted by the Pew Research Center in 2010 and released January 2011[19] found that there are 1.62 billion Muslims around the world, and it is estimated over 75–90% are Sunni.[20]

Islam does not have a formal hierarchy or clergy. Leaders are informal, and gain influence through study to become a scholar of Islamic law, called sharia. According to the Islamic Center of Columbia, South Carolina, anyone with the intelligence and the will can become an Islamic scholar. During Midday Mosque services on Fridays, the congregation will choose a well-educated person to lead the service, known as a Khateeb (one who speaks).[21]

There are several intellectual traditions within the field of Islamic law, often referred to as legal schools. These varied traditions reflect differing viewpoints on some laws and obligations within Islamic law. While one school may see a certain act as a religious obligation, another may see the same act as optional. These schools aren't regarded as sects; rather, they represent differing viewpoints on issues that are not considered the core of Islamic belief.

Historians have differed regarding the exact delineation of the schools based on the underlying principles they follow. Many traditional scholars saw Sunni Islam in two groups: Ahl al-Ra'i, or "people of reason," due to their emphasis on scholarly judgment and discourse; and Ahl al-Hadith, or "people of traditions," due to their emphasis on restricting juristic thought to only what is found in scripture.[22]Ibn Khaldun defined the Sunni schools as three: the Hanafi school representing reason, the Ẓāhirīte school representing tradition, and a broader, middle school encompassing the Shafi'ite, Malikite and Hanbalite schools.[23][24]

The Great Mosque of Kairouan (also known as the Mosque of Uqba) was, in particular during the 9th, 10th and 11th centuries, an important center of Islamic learning with an emphasis on the Maliki Madh'hab.[29] It is located in the city of Kairouan in Tunisia

Interpreting Islamic law by deriving specific rulings – such as how to pray – is commonly known as Islamic jurisprudence. The schools of law all have their own particular tradition of interpreting this jurisprudence. As these schools represent clearly spelled out methodologies for interpreting Islamic law, there has been little change in the methodology with regard to each school. While conflict between the schools was often violent in the past,[26] today the schools recognize one another as viable legal methods rather than sources of error or heresy in contrast to one another. Each school has its evidences, and differences of opinion are generally respected.

Some Islamic scholars faced questions that they felt were not explicitly answered in the Quran and the Sunnah, especially questions with regard to philosophical conundra such as the nature of God, the existence of human free will, or the eternal existence of the Quran. Various schools of theology and philosophy developed to answer these questions, each claiming to be true to the Quran and the Muslim tradition (sunnah). Among Sunni Muslims, various schools of thought in theology began to be born out of the sciences of kalam in opposition to the textualists who stood by affirming texts without delving into philosophical speculation as they saw it as an innovation in Islam. The following were the three dominant schools of theology that grew. All three of these are accepted by Muslims around the globe, and are considered within "Islamic orthodoxy". The key beliefs of Sunni Islam are all agreed upon (being the six pillars of Iman) and codified in the treatise on Aqeedah by Imam Ahmad ibn Muhammad al-Tahawi in his Aqeedat Tahawiyyah.

Founded by Abu al-Hasan al-Ash'ari (873–935). This theological school of Aqeedah was embraced by many Muslim scholars and developed in parts of the Islamic world throughout history; the Imam al-Ghazali wrote on the creed discussing it and agreeing upon some of its principles.[31]

Ash'ari theology stresses divine revelation over human reason. Contrary to the Mu'tazilites, they say that ethics cannot be derived from human reason, but that God's commands, as revealed in the Quran and the Sunnah (the practices of Muhammad and his companions as recorded in the traditions, or hadith), are the sole source of all morality and ethics.

Regarding the nature of God and the divine attributes, the Ash'ari rejected the Mu'tazili position that all Quranic references to God as having real attributes were metaphorical. The Ash'aris insisted that these attributes were as they "best befit His Majesty". The Arabic language is a wide language in which one word can have 15 different meanings, so the Ash'aris endeavor to find the meaning that best befits God and is not contradicted by the Quran. Therefore, when God states in the Quran, "He who does not resemble any of His creation," this clearly means that God cannot be attributed with body parts because He created body parts. Ash'aris tend to stress divine omnipotence over human free will and they believe that the Quran is eternal and uncreated.

Traditionalist theology is a movement of Islamic scholars who reject rationalistic Islamic theology (kalam) in favor of strict textualism in interpreting the Quran and sunnah.[33] The name derives from "tradition" in its technical sense as translation of the Arabic word hadith. It is also sometimes referred to by several other names.

Adherents of traditionalist theology believe that the zahir (literal, apparent) meaning of the Qur'an and the hadith have sole authority in matters of belief and law; and that the use of rational disputation is forbidden even if it verifies the truth.[34] They engage in a literal reading of the Qur'an, as opposed to one engaged in ta'wil (metaphorical interpretation). They do not attempt to conceptualize the meanings of the Qur'an rationally, and believe that their realities should be consigned to God alone (tafwid).[35] In essence, the text of the Qur'an and Hadith is accepted without asking "how" or "Bi-la kaifa".

Traditionalist theology emerged among scholars of hadith who eventually coalesced into a movement called ahl al-hadith under the leadership of Ahmad ibn Hanbal.[36] In matters of faith, they were pitted against Mu'tazilites and other theological currents, condemning many points of their doctrine as well as the rationalistic methods they used in defending them.[36] In the tenth century al-Ash'ari and al-Maturidi found a middle ground between Mu'tazilite rationalism and Hanbalite literalism, using the rationalistic methods championed by Mu'tazilites to defend most tenets of the traditionalist doctrine.[37][38] Although the mainly Hanbali scholars who rejected this synthesis were in the minority, their emotive, narrative-based approach to faith remained influential among the urban masses in some areas, particularly in AbbasidBaghdad.[39]

While Ash'arism and Maturidism are often called the Sunni "orthodoxy", traditionalist theology has thrived alongside it, laying rival claims to be the orthodox Sunni faith.[40] In the modern era it has had a disproportionate impact on Islamic theology, having been appropriated by Wahhabi and other traditionalist Salafi currents and spread well beyond the confines of the Hanbali school of law.[41]

The Quran as it exists today in book form was compiled by Muhammad's companions (Sahabah) within a handful of months of his death, and is accepted by all sects of Islam. However, there were many matters of belief and daily life that were not directly prescribed in the Quran, but were actions that were observed by Muhammad and the early Muslim community. Later generations sought out oral traditions regarding the early history of Islam, and the practices of Muhammad and his first followers, and wrote them down so that they might be preserved. These recorded oral traditions are called hadith. Muslim scholars have through the ages sifted through the hadith and evaluated the chain of narrations of each tradition, scrutinizing the trustworthiness of the narrators and judging the strength of each hadith accordingly.

Kutub al-Sittah are six books containing collections of hadiths. Sunni Muslims accept the hadith collections of Bukhari and Muslim as the most authentic (sahih, or correct), and while accepting all hadiths verified as authentic, grant a slightly lesser status to the collections of other recorders. There are, however, four other collections of hadith that are also held in particular reverence by Sunni Muslims, making a total of six:

^Hughes, Aaron. Muslim Identities: An Introduction to Islam. p. 115. It is a mistake to assume as is commonly done that Sunni Islam arose as normative from the chaotic period following Muhammad's(Sallahu Alaihi Wasallim) death... This mistake is based in... the taking of later and often highly ideological sources as accurate historical portrayals - and in part on the fact that the overwhelming majority of Muslims throughout the world follows now what emerged as Sunni Islam...

^Minahan, James (2002). Encyclopedia of the Stateless Nations. p. 547.

^Source for distribution is the CIA World Factbook, Shiite/Sunnite distribution collected from other sources. Shiites may be underrepresented in some countries where they do not appear in official statistics.

^Halverson, Jeffry R. (2010). Theology and Creed in Sunni Islam: The Muslim Brotherhood, Ash'arism, and Political Sunnism. Palgrave Macmillan. p. 36. ISBN9781137473578. The Atharis can thus be described as a school or movement led by a contingent of scholars (ulama), typically Hanbalite or even Shafi'ite, which retained influence, or at the very least a shared sentiment and conception of piety, well beyond the limited range of Hanbalite communities. This body of scholars continued to reject theology in favor of strict textualism well after Ash'arism had infiltrated the Sunni schools of law. It is for these reasons that we must delineate the existence of a distinctly traditionalist, anti-theological movement, which defies strict identtification with any particular madhhab, and therefore cannot be described as Hanbalite.

^Brown, Jonathan A.C. (2009). Hadith: Muhammad's Legacy in the Medieval and Modern World. Oneworld Publications (Kindle edition). p. 180. The Ash‘ari school of theology is often called the Sunni 'orthodoxy.' But the original ahl al-hadith, early Sunni creed from which Ash‘arism evolved has continued to thrive alongside it as a rival Sunni 'orthodoxy' as well.